The Gateway is not using a cipher suite based upon Diffie-Hellman key exchange.The Gateway is acting as the server in a TCP connection.This article has the following limitations: What is the source IP address? The destination IP address?Ĭ.Background Wireshark can be used to decode and decrypt SSL-TLS-encrypted communications between a client application and the CA API Gateway appliance. List the types of headers included in this message, in order.ī. Locate the correct message, and answer the following questions:Ī. Recall that there are several layers of headers encapsulating this payload, so you’ll need to look at the deepest layer in the message to find the Web page’s data. At some point later in the conversation, locate an HTTP/XML message that contains the actual data for Google’s search page. The three-way handshake establishes the session, but the conversation continues as the Web server begins to respond to your browser’s request for the Web page. Locate the third message in this three-way handshake, the message, and answer the following questions:ġ2. Which flags are set in the TCP segment?ġ1. What is the sequence number? The acknowledgment number? c. What is the source IP address? The destination IP address?ī. Immediately after that initial message, locate the message and answer the following questions:Ī. Close the Follow TCP Stream dialog box that opens, as you will be examining data in the actual capture.ġ0. Rightclick the message and click Follow TCP Stream. Apply another filter layer to show only the messages for this TCP conversation. Look back at the relative numbers shown in Figure 3-27, and compare the data in that figure to the random numbers shown in Figure 3-28.ĩ. Switch the output to show the actual, random numbers (in decimal form) in your capture by clicking on the Edit menu, then click Preferences, expand the Protocols list, click TCP, and uncheck Relative sequence numbers. The actual value is presented in hexadecimal format.Ĩ. To find the actual, random sequence number assigned to this segment, click on the sequence number field in the second pane, then find the corresponding value now highlighted in the third pane. Random numbers, on the other hand, are more difficult to fake.ħ. Relative numbers are easier for humans to keep up with, but they provide no security in that they’re very predictable.
That’s because Wireshark shows relative numbers instead of the actual, random numbers used in the segments themselves.
Which flags are set in the TCP segment? If you’re using the default settings in Wireshark, you probably found a sequence number of 1. Open the TCP segment header in the second pane, and answer the following questions:ī. Now check your filter results for the first message after this DNS request. What is the source port? The destination port?Ħ. If the message used IPv4, what was the TTL? If IPv6, what was the hop limit?Į. Once you’ve located this message, click on it and examine the details of the message in the second pane. You’ll see DNS in the Protocol field, and something to the effect of “Standard query” and “in the Info field, as shown in Figure 3-27.ĥ. But you’ll still probably have to scroll through your results to find exactly the right DNS message that started this process. This filter helps reduce the number of messages to the ones you actually want to see. Apply the following filter to your capture:Ĥ. Because your transmission has to do with requesting a Web page, you need to filter to port 80.
WIRESHARK HTTP DECODE SERIES
A series of TCP messages will then show the three-way handshake, along with the rest of the data transmission. Somewhere in your capture, a DNS message will show the original request to resolve the name to its IP address. Now apply a filter to expose the messages involved with your Web site request. You’ll have fewer messages to sort through if you can do this entire process fairly quickly.ģ. Once the page loads, stop the Wireshark capture. Alternately, you can drag a window to one side of your screen until it snaps into position.Ģ. In Windows, you can quickly snap a window to one side of your screen by holding down the Win key on your keyboard, pressing either the left or right arrow key, then releasing both keys. Open a browser and snap that window to the other side of your screen so you can see both windows. Open Wireshark and snap the window to one side of your screen. In this project, you use Wireshark to capture your own HTTP messages, examine the TCP headers, and practice interpreting the data you’ll find there.ġ. In this chapter, you walked through a TCP segment to interpret the data included in its header. Decode a TCP Segment in a Wireshark Capture
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